An electromagnetic waveguide is a structure for conducting electromagnetic waves. Typically these waveguides are rectangular in cross-section, rigid, and constructed of conductive material. Such a waveguide generally serves as an interconnect from one RF component or source to another RF component or load. One example system where components are typically interconnected using waveguides is in communication satellites.
Achieving sufficient RF power in satellite communication systems may require operating power amplifiers, such at TWT (traveling wave tube) systems, in parallel. When operated in parallel, the signals from multiple TWTs may require phase and amplitude adjustments in order to be combined coherently. One technique for achieving the required phase shifting and amplitude attenuation is based on Fox type phase shifters and rotary vane attenuators. Internally, these components generally use circular waveguides. Size limitations in satellite applications often demand interconnecting the Fox type phase splitter and the rotary vane attenuator with circular waveguides.
Traditional circular waveguides operate sufficiently for interconnecting Fox type phase shifters and rotary vane attenuators if the components are connected in a straight line or end-to-end. However, the size limitations mentioned above also create a desire to bend the waveguides and effectively fold the circuit into a more compact assembly. Unfortunately, placing a bend into a circular waveguide can introduce problems.
Circular (or even square) waveguides differ from conventional rectangular waveguides in that two orthogonal modes or polarizations can propagate within the circular (or square) waveguide. Bends or discontinuities in the waveguide can cause coupling between these two orthogonal modes causing degradation of the desired signal.
Furthermore, bent waveguides are generally complex to manufacture requiring casting or split machining followed by brazing. Such manufacturing techniques require considerable material handling, and multiple additional steps such as brazing the segments of the waveguide together and final clean-up machining to form the waveguide bend.
In light of the complications and limitations introduced by attempts to form bends in compact circular waveguides, there is a need for a circular waveguide that is both compact and able to propagate radio frequency waves around a bend without excessive signal degradation. Furthermore, there is a need to manufacture such a compact circular waveguide as quickly and as simply as possible. As such, there is a need for a circular waveguide bend that can be machined from a single piece of metal stock with the tool, such as an end mill cutter, entering the piece only from the flange ends.